Effects of Oxygen Partial Pressure on Oxidation Behavior of CMnSi TRIP Steel in an Oxidation-Reduction Scheme

( Seong-hwan Kim ),( Joo-youl Huh ),( Myung-soo Kim ),( Jong-sang Kim ) 한국부식방식학회(구 한국부식학회) 2017 Corrosion Science and Technology Vol.16 No.1

An oxidation-reduction scheme is an alternative approach for improving the galvanizability of advanced high-strength steel in the continuous hot-dip galvanizing process. Here, we investigated the effect of oxygen partial pressure (PO₂) on the oxidation behavior of a transformation-induced plasticity steel containing 1.5 wt% Si and 1.6 wt% Mn during heating to and holding for 60 s at 700 °C under atmospheres with various PO₂ values. Irrespective of PO₂, a thin amorphous Si-rich layer of Si-Mn-O was formed underneath the Fe oxide scale (a Fe₂O₃/Fe₃O₄ bilayer) in the heating stage. In contrast to Si, Mn tended to segregate at the scale surface as (Fe,Mn)₂O₃. The multilayered structure of (Fe,Mn)₂O₃/Fe₂O₃/Fe₃O₄/amorphous Si-Mn-O remained even after extended oxidizing at 700 °C for 60 s. Fe₂O₃ was the dominantly growing oxide phase in the scale. The enhanced growth rate of Fe₂O₃ with increasing PO₂ resulted in the formation of more Kirkendall voids in the amorphous Si-rich layer and a less Mn segregation at the scale surface. The mechanisms underlying the absence of FeO and the formation of Kirkendall voids are discussed.

Ru 촉매에서의 암모니아 부분산화에 대한 연구

이상호,장형준,박철웅,오세철,이선엽,김용래 한국수소및신에너지학회 2022 한국수소 및 신에너지학회논문집 Vol.33 No.6

Green ammonia is a promising renewable energy carrier. Green ammonia can be used in various energy conversion devices (e.g., engine, fuel cell, etc.). Ammonia has to be fed with hydrogen for start-up and failure protection of some energy conversion devices. Ammonia can be converted into hydrogen by decomposition and partial oxidation. Especially, partial oxidation has the advantages of fast start-up, thermally self-sustaining operation and compact size. In this paper, thermodynamics, start-up and operation characteristics of ammonia partial oxidation were investigated. O2/NH3 ratio, ammonia flow rate and catalyst volume were varied as operation parameters. In thermodynamic analysis, ammonia conversion was maximized in the O2/NH3 range from 0.10 to 0.15. Ammonia partial oxidation reactor was successfully started using 12 V glow plug. At 0.13 of O2/HN3 ratio and 10 LPM of ammonia flow rate, ammonia partial oxidation reactor showed 90% of ammonia conversion over commercial Ru catalyst. In addition, Increasing O2/NH3 ratio from 0.10 to 0.13 was more effective for high ammonia conversion than increasing catalyst volume at 0.10 of O2/NH3.

Syngas production on a Ni-enhanced Fe₂O₃/Al₂O₃ oxygen carrier via chemical looping partial oxidation with dry reforming of methane

Kang, Dohyung,Lim, Hyun Suk,Lee, Minbeom,Lee, Jae W. Elsevier 2018 APPLIED ENERGY Vol.211 No.-

<P><B>Abstract</B></P> <P>A novel chemical looping process was introduced by combining partial oxidation and dry reforming of methane on a cost-effective iron-based oxygen carrier to produce high-purity syngas with a H<SUB>2</SUB>/CO ratio of 2. The rationale for the proposed chemical looping process was substantiated with the thermodynamic data, which showed increased syngas purity and an H<SUB>2</SUB>/CO ratio close to 2 by introducing the CH<SUB>4</SUB>-CO<SUB>2</SUB> mixture feed. Compared with the general chemical looping process, the calculated carbon deposition with the CO<SUB>2</SUB> emission of the proposed process was dramatically decreased by using CO<SUB>2</SUB> as a co-feed with CH<SUB>4</SUB>. Due to the exothermic heat from the oxidation reaction of the oxygen carrier, the net heat duty of the novel chemical looping process was much lower than that of the dry reforming process. To validate the thermodynamic results, a Ni entrapped Fe<SUB>2</SUB>O<SUB>3</SUB>/Al<SUB>2</SUB>O<SUB>3</SUB> oxygen carrier was synthesized by increasing the metal-support interaction through a sol-gel route. It is striking that the formation of Ni aluminate phase in the Ni-reinforced oxygen carrier facilitated dry reforming with partial oxidation while suppressing methane decomposition. By supplying a nonstoichiometric CH<SUB>4</SUB>-CO<SUB>2</SUB> mixture feed (CO<SUB>2</SUB>/CH<SUB>4</SUB> ratio = 0.38) to the 1 wt% Ni-entrapped Fe<SUB>2</SUB>O<SUB>3</SUB>/Al<SUB>2</SUB>O<SUB>3</SUB> oxygen carrier at 900 °C, an H<SUB>2</SUB>/CO ratio of 2.09 and high CO selectivity of 96.76% were achieved with minimized carbon deposition. These results were close to the calculated equilibrium value while a Ni-impregnated Fe<SUB>2</SUB>O<SUB>3</SUB>/Al<SUB>2</SUB>O<SUB>3</SUB> oxygen carrier showed an increased H<SUB>2</SUB>/CO ratio of 2.36 with severe carbon deposition by the promoted methane decomposition. In addition, the Ni-reinforced oxygen carrier also showed stable redox activity during successive reduction and oxidation cycles.</P> <P><B>Highlights</B></P> <P> <UL> <LI> CLPD was derived by merging dry reforming into chemical looping partial oxidation. </LI> <LI> Results of CLPD were calculated using the ASPEN Plus simulator. </LI> <LI> Syngas with a H<SUB>2</SUB>/CO ratio of 2 was produced through the CLPD process. </LI> <LI> Ni-enhanced Fe<SUB>2</SUB>O<SUB>3</SUB>/Al<SUB>2</SUB>O<SUB>3</SUB> showed the enhanced CLPD activity without rare earth metals. </LI> <LI> Stabilized Ni in Al<SUB>2</SUB>O<SUB>3</SUB> promoted dry reforming with suppressed carbon deposition. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

메탄의 균일 및 접촉부분산화에 의한 메탄올 합성

최우진 ( Woo Jin Choi ),황재영 ( Jae Young Hwang ),안성환 ( Sung Hwan Ahn ),김명수 ( Myung Soo Kim ),박홍수 ( Hong Soo Park ),함현식 ( Hyun Sik Hahm ) 한국유화학회 2005 한국응용과학기술학회지 Vol.22 No.1

N/A Methanol was synthesized by homogeneous and catalytic reactions of partial oxidation of methane. The effect of pressure, temperature and oxygen concentration on methanol synthesis was investigated. The catalyst used was Bi-Cs-Mg-Cu-Mo mixed oxide. The partial oxidation reaction was carried out in a fixed bed reactor at 20~46 bar and 450~480℃ and oxygen concentration of 5.3~7.7 ㏖%. The results were compared with results of homogeneous reaction performed at the same conditions. Methane conversions of the homogeneous and catalytic reactions increased with temperature. Methanol selectivity of the homogeneous reaction decreased with increasing temperature. However, the methanol selectivity of catalytic reaction increased with temperature. For both homogeneous and catalytic reactions, the methane conversions were around 5 %. This may be due to the low oxygen concentration. Methanol selectivity of the catalytic reaction was higher than that of homogeneous one.

Vapor-phase Oxidation of Alkylaromatics over V/TiO2 andVSb/Al2O3 Catalysts: Effect of Alkali Metals

윤지웅,정성화,Jong-San Chang* 대한화학회 2007 Bulletin of the Korean Chemical Society Vol.28 No.12

Oxidation of alkylaromatics including toluene and p-methoxytoluene has been carried out over alkali metal (AM)-containing catalysts such as AM-V/TiO2 and AM-VSb/Al2O3 in vapor-phase using oxygen as an oxidant. The selectivity for partial oxidations increases with incorporation of an alkali metal or with increasing the basicity of alkali metals (from Na to Cs), irrespective of the supports or reactants. However, the conversion is nearly constant or slightly decreasing with the addition of alkali metals in the catalyst. The increased selectivity may be related with the decreased acidity even though more detailed work is necessary to understand the effect of alkali metals in the oxidation. The AM-VSb/Al2O3 may be suggested as a potential selective catalyst for vapor-phase oxidations.

Vapor-phase Oxidation of Alkylaromatics over V/TiO₂ and VSb/Al₂O₃ Catalysts: Effect of Alkali Metals

Yoon, Ji-Woong,Jhung, Sung-Hwa,Chang, Jong-San Korean Chemical Society 2007 Bulletin of the Korean Chemical Society Vol.28 No.12

Oxidation of alkylaromatics including toluene and p-methoxytoluene has been carried out over alkali metal (AM)-containing catalysts such as AM-V/TiO2 and AM-VSb/Al2O3 in vapor-phase using oxygen as an oxidant. The selectivity for partial oxidations increases with incorporation of an alkali metal or with increasing the basicity of alkali metals (from Na to Cs), irrespective of the supports or reactants. However, the conversion is nearly constant or slightly decreasing with the addition of alkali metals in the catalyst. The increased selectivity may be related with the decreased acidity even though more detailed work is necessary to understand the effect of alkali metals in the oxidation. The AM-VSb/Al2O3 may be suggested as a potential selective catalyst for vapor-phase oxidations.

Stabilization of extra rich CH4/O2 flame in a two-section porous medium and the thermal partial oxidation characteristics thereof

곽영태,이대근,고창복 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.10

Fuel-rich CH 4 /O 2 flames in a two-section porous medium burner were experimentally investigated for its application to the production of high concentration H 2 /CO syngas. The burner was made up of two axially-stacked silicon carbide foams having different pore sizes. Various flame behaviors, such as stable flame, flashback and blowout, were observed and, for the stable flame, temperature distributions and reformate compositions were measured. Results showed that the flame was stable in a sideway V-shape region on the domain of equivalence ratio and filtration velocity. Especially, it was found that the maximum equivalence ratio of the upper stable region was larger than the fuel-rich flammability limit showing characteristics of submerged combustion in porous media, which made the reaction closer to the stoichiometric partial oxidation. The reformate composition was measured for various conditions and maximum mole fraction of H 2 and CO was 55.5 % and 28.0 % in dry basis being much higher than the air oxidant case. From these results, the reforming performance such as CH 4 conversion, selectivity and yield of H 2 , CO, and energy conversion efficiency were evaluated. The equilibrium and the adiabatic planar flame were simulated as references to investigate the characteristics of partial oxidation reforming. The results may indicate that the porous media burner can be practically applied in producing high concentration H 2 /CO syngas, if it is designed to ensure minimum heat loss and enough residence time.

Research on room temperature methane oxidation

문준혁 한국공업화학회 2019 한국공업화학회 연구논문 초록집 Vol.2019 No.0

Methane is representative gas that accounts for more than 95% of natural gas components and causes climate change. Therefore, the technology for converting methane into high value-added chemicals has a large impact on the environment as well as on the industry. Traditionally, methane has been converted to syngas produced through a hot wet or dry reforming process to produce various alcohols, aldehydes, olefins, and aromatics. Despite the development of various catalysts and process optimization, the reaction to produce syngas still requires very high temperatures. Thus much efforts have been devoted to producing chemical products directly at relatively low temperatures by partial oxidation of methane. These efforts led to the development of new oxidizing agents or catalysts with low activation energy. In this presentation, we introduce recent atypical low temperature methane oxidation.

Partially reversible Li₂O formation in ZnO: A critical finding supporting realization of highly reversible metal oxide electrodes

Park, M.G.,Sung, G.K.,Sung, N.E.,Kim, J.H.,Park, C.M. Elsevier Sequoia 2016 Journal of Power Sources Vol.328 No.-

The electrochemical reaction mechanism of ZnO is investigated to understand its Li insertion/extraction behavior using ex situ X-ray diffraction, extended X-ray absorption fine structure, and high-resolution transmission electron microscopy. Based on these analyses, an interesting partial recombination reaction of ZnO is discovered, which demonstrates that Li<SUB>2</SUB>O formed during Li insertion is partially reversible. Additionally, we discover that the control of the partial recombination reaction of the metal oxide is very important for improving reversibility in the first cycle, which is a key finding for realization of highly reversible oxide-based electrode materials. In addition, to enhance the electrochemical performance of the ZnO electrode, a nanostructured ZnO/C composite is prepared by a simple high-energy mechanical milling process. This process allows the electrochemical performance of the ZnO electrode to be evaluated as an anode for rechargeable Li-ion batteries. Electrochemical tests show that the nanocomposite electrode exhibits a high initial charge capacity of 682 mAh g<SUP>-1</SUP>, fast rate capability of 371 mAh g<SUP>-1</SUP> at 2 C, and excellent cyclability over 200 cycles.

예혼합압축착화엔진의 부분 산화 개질을 이용한 고체산화물 연료전지 발전시스템 모델링 연구 및 가용에너지 분석

오세철(Sechul Oh),김선엽(Seonyeob Kim),최원재(Wonjae Choi),송한호(Han Ho Song) 대한기계학회 2014 대한기계학회 춘추학술대회 Vol.2014 No.11

Due to the depletion of fossil fuels and environmental issues such as atmosphere pollution, fuel cell power generation system with high efficiency and low emission is being pursued. Traditionally, pre-reforming system, such as steam reforming, has been used in almost every fuel cell system to produce hydrogen as the fuel. We studied the use of homogeneous charge compression ignition engine as an external reformer for the fuel cell system, whose operation occurs in an excessively rich condition leading to un-catalyzed in-cylinder partial oxidation. An exergy analysis was performed to compare HCCI reforming system with steam reforming one. From the results, it was shown that the fuel-air mixture was not fully reformed in HCCI reforming system, because the exhaust stream is not in the equilibrium state, while we should operate it at O/C > 0.8. The efficiency and power output of HCCI reforming system showed that the efficiency of HCCI reforming system is greater due to the heat balance of each system, although the power output of HCCI reforming system is relatively small as compared to that in steam reforming system.